We found this circuit in a 1956 Sylvania publication. It serves to monitor telegraph transmissions being placed next to the transmitter. The circuit is indicated for the range of 80 and 160 meters.
The four gates of a 40111 IC are used in thes two-out circuit. The output chages their state in a...
This circuit was found in a 1980 publication. It uses only 3 easily obtainable transistors. It is a...
This circuit operates at a voltage of 1.3 V from a single mercury cell. We found in an old...